Maurice W. Harmon

Antiviral Activity of Intranasally Applied Human Leukocyte Interferon

Previous studies in our laboratory have demonstrated that the development of antiviral activity of human leukocyte interferon (IF) in nasal epithelial cells is time and concentration dependent and that the loss of intranasally applied human leukocyte IF is rapid. The present studies compared the activity of IF applied intranasally either by nasal drops or by a saturated cotton pledget. Adult volunteers had IF applied to an area of nasal mucosa (2 by 2 cm2) either by repeated nose drops or by a saturated cotton pledget that was applied to the nasal mucosa and left in place for 1 h. Nasal epithelial cells scraped from the area of application, as well as the control, untreated side of the same volunteers, were challenged with vesicular stomatitis virus. No significant reduction in mean virus yield was found in volunteers who received 80,000 U by nose drops. Significant reduction (P < 0.025) in mean virus yield was found in cells obtained 4 h after 80,000, 50,000, or 20,000 U was applied by cotton pledget or in volunteers pretreated with oral antihistamines prior to receiving 80,000 U by nose drops. These experiments indicate that nasal epithelial cells can be made antiviral in vivo by application of human leukocyte IF. However, practical usefulness of human leukocyte IF for prophylaxis against respiratory viral infections may depend on the method of local application.

Expression of influenza A and B virus nucleoprotein antigens in baculovirus.

Full-length cDNA clones of the nucleoprotein (NP) genes of influenza A/Ann Arbor/6/60 and B/Ann Arbor/1/86 viruses were constructed from virion RNA and subsequently expressed in Spodoptera frugiperda (Sf9) cells using the baculovirus vector, Autographa californica nuclear polyhedrosis virus. Western blot analysis of lysates prepared from Sf9 cells infected with the recombinant viruses confirmed that the baculovirus-expressed NP antigens were reactive with monoclonal antibodies specific for either type A or B NP and with anti-NP antibodies in human serum samples. Electrophoretic analysis indicated that the expressed NP antigens comigrated with NP purified from influenza A or B virions and that the recombinant NP antigens represented greater than 10% of total protein in infected cells. Dilutions of clarified Sf9 cell lysates were used as antigens in a standard enzyme immunoassay to detect serum antibody specific for influenza A or B viruses. The results from assays using the baculovirus-expressed NP antigens showed good correlation with the results obtained using bacterially expressed NP antigen as well as complement fixation. Therefore, baculovirus-expressed NP antigens have the potential to be used to develop reproducible and routine assays for the serodiagnosis of influenza virus infections as an alternative to the complement fixation or haemagglutination inhibition tests.

Post-Exposure Prophylaxis of Murine Rabies with Polyinosinic-Polycytidylic Acid and Chlorite-Oxidized Amylose

Chlorite-oxidized amylose (COAM), polyinosinic-polycytidylic acid [poly(I:C)], and combinations of the two drugs were evaluated for their interferon-inducing properties and their ability to protect mice against rabies infection. Post-exposure administration of one or two doses (100 μg each) of poly(I:C) significantly protected mice against rabies infection. Pretreatment of mice with COAM 3 h before poly(I:C) stimulation resulted in an enhancement of the interferon response. However, the increased interferon titers were not reflected by increased protection against rabies infection over that achieved with poly(I:C) therapy alone. Therapy with COAM alone did not protect mice against rabies but, rather, was associated with enhanced mortality.

Rapid onset of the interferon-induced antiviral state in human nasal epithelial and foreskin fibroblast cells.

Summary This report describes a cell culture system with nasal epithelial (NE) cells in which the interferon (IF) response of these cells was compared with the IF response of human foreskin fibroblast (HFF) cells. The antiviral state that developed in NE cells after exposure to human leukocyte IF was less than the antiviral state that developed in HFF cells. In addition, the slope of the dose-response curve for HFF cells was greater than that for NE cells. It could be demonstrated that the antiviral state developed rapidly in NE cells following a brief (15-min) exposure to IF at 34°C provided a high IF concentration was used. Two respiratory viruses were tested for sensitivity to the IF-induced antiviral state that develops in NE cells. Both coxsackievirus A type 21 and parainfluenza virus type 3 were slightly less sensitive to the IF-induced antiviral state in NE cells compared to vesicular stomatitis virus. We sincerely appreciate the excellent technical assistance of Michéle Pelanne. This work was supported by Public Health Service Contracts AI 42530 and AI 32506 from the Development and Applications Branch, National Institute of Allergy and Infectious Diseases.